Agricultural sprayers have been known and used for many years in applying a variety of chemical products to agricultural crops. A typical sprayer of the kind is towed by a tractor and includes a tank for receiving a supply of water and the desired agricultural chemical, mixed in accordance with a predetermined proportion. The sprayer carries spray nozzles configured to dispense and direct a liquid spray toward the particular agricultural products for which the spray is intended. The water and chemical mixture is supplied from the tank to the nozzles by a pump, which is typically driven by power takeoff from the tractor towing the sprayer.
The term "agricultural product" as used herein refers to orchards and groves in which trees bearing fruit or other products are the target of the spray, as well as row crops in which the crop being sprayed grows in rows and is relatively close to the ground. Those skilled in the art will know that the spray nozzles and related elements for directing the spray toward the intended target may vary depending on the intended used for which a particular sprayer is designed.
Agricultural chemicals intended for spray delivery usually are purchased in dry or powder form, for reasons of economy. The sprayer operator loads into the sprayer tank the desired chemical at a quantity determined to provide the desired chemical concentration, when the tank is filled with water to a predetermined operating capacity. This filling operation in practice typically takes place near a well or other source of water, which may be at some remote point from the grove or other location where the spraying will take place. Because the dry chemicals must be completely mixed with the water to produce a spray solution of the desired concentration, the tank of the typical agricultural sprayer is equipped with mixing paddles mounted on a rotatable shaft extending through the tank. This shaft is coupled to the power takeoff drive from the tractor. As the sprayer operator drives from the loading location to the point where spraying will commence, the shaft rotates within the tank so that the paddles agitate the liquid therein and help dissolve the dry chemical into solution with the liquid. The liquid delivery line from the sprayer to the spray nozzles may include a filter to prevent undissolved chemical and other particulate matter from reaching the spray nozzles, so as to prevent clogging the nozzles with solid particles.
The trend in agricultural sprayers is to operate the sprayer with a higher chemical concentration, combined with reducing the volume of spray emitted from the spray nozzles and directed toward the target of the spray. Reducing the volume of the liquid spray reduces the amount of airborne overspray that may overspray or otherwise miss the intended target. Because the spray at increased concentration is applied at a lower volume, the amount of the chemicals applied to the target is not substantially different from the amount supplied by higher-volume sprayers operating at a lower chemical concentration. The sprayers delivering a reduced volume of spray per acre (or other measure) also is more economical for the farmer, as the reduced delivery rate of the mixture in the sprayer tank yields a longer time between refills and thus reduces the amount of down-time required to spray a particular acreage.
Agricultural sprayers operating at a higher chemical concentration have a correspondingly greater need for all the chemical to enter into solution with the water in the spray tank. Because the delivery rate of the spray is reduced in high concentration sprayers, a given proportion of undissolved chemical causes a more significant reduction in the amount of chemical delivered to the target than in a conventional higher-volume sprayer. This reduces the effectiveness of the spraying operation and also constitutes a direct economic loss, because any undissolved chemical is wasted. Moreover, clogging the spray nozzles is an even greater problem because of the smaller orifices used in the spray nozzles of low-volume sprayers.